Method and apparatus for performing an open wedge osteotomy

ABSTRACT

A method and apparatus for performing an open wedge osteotomy utilizing a keyed, wedge-shaped implant for disposition in a keyed, wedge-shaped opening created in a bone. The keys may be disposed in vertical or horizontal arrangements. In addition, a shear rib key hole may be formed adjacent the wedge-shaped opening in the bone.

REFERENCE TO PENDING PRIOR PATENT APPLICATIONS

This patent application is a divisional of U.S. patent application Ser.No. 11/607,321, filed Dec. 1, 2006, now U.S. Pat. No. ______, which:

(i) is a continuation-in-part of pending prior U.S. patent applicationSer. No. 11/047,159, filed Jan. 31, 2005 by Vincent P. Novak for OPENWEDGE OSTEOTOMY SYSTEM AND SURGICAL METHOD;

(ii) is a continuation-in-part of pending prior U.S. patent applicationSer. No. 11/047,551, filed Jan. 31, 2005 by Vincent P. Novak for OPENWEDGE OSTEOTOMY SYSTEM AND SURGICAL METHOD;

(iii) is a continuation-in-part of pending prior U.S. patent applicationSer. No. 11/352,103, filed Feb. 9, 2006 by Vincent P. Novak et al. forMULTI-PART IMPLANT FOR OPEN WEDGE KNEE OSTEOTOMIES;

(iv) is a continuation-in-part of pending prior U.S. patent applicationSer. No. 11/350,333, filed Feb. 8, 2006 by Vincent P. Novak et al. forMETHOD AND APPARATUS FOR FORMING A WEDGE-LIKE OPENING IN A BONE FOR ANOPEN WEDGE OSTEOTOMY;

(v) is a continuation-in-part of pending prior U.S. patent applicationSer. No. 11/396,490, filed Apr. 3, 2006 by Kelly Ammann et al. forMETHOD AND APPARATUS FOR PERFORMING AN OPEN WEDGE, HIGH TIBIALOSTEOTOMY;

(vi) claims benefit of pending prior U.S. Provisional Patent ApplicationSer. No. 60/741,313, filed Dec. 1, 2005 by Kelly Ammann et al. forMETHOD AND SYSTEM OF FIXATION FOR PERFORMING AN OPENING WEDGE OSTEOTOMY;

(vii) claims benefit of pending prior U.S. Provisional PatentApplication Ser. No. 60/742,772, filed Dec. 6, 2005 by Kelly G. Ammannet al. for METHOD AND SYSTEM OF FIXATION FOR PERFORMING AN OPENING WEDGEOSTEOTOMY;

(viii) claims benefit of pending prior U.S. Provisional PatentApplication Ser. No. 60/753,366, filed Dec. 22, 2005 by Kelly G. Ammannet al. for METHOD AND SYSTEM OF FIXATION FOR PERFORMING AN OPENING WEDGEOSTEOTOMY;

(ix) claims benefit of pending prior U.S. Provisional Patent ApplicationSer. No. 60/835,172, filed Aug. 2, 2006 by Kelly G. Ammann et al. forMETHOD AND SYSTEM OF FIXATION FOR PERFORMING AN OPENING WEDGE OSTEOTOMY;

(x) claims benefit of pending prior U.S. Provisional Patent ApplicationSer. No. 60/835,269, filed Aug. 3, 2006 by Kelly G. Ammann et al. forMETHOD AND SYSTEM OF FIXATION FOR PERFORMING AN OPENING WEDGE OSTEOTOMY;

(xi) claims benefit of pending prior U.S. Provisional Patent ApplicationSer. No. 60/835,292, filed Aug. 3, 2006 by Robert E. Schneider et al.for BONE ANCHOR FOR FIXATION TO A DISTAL CORTICAL WALL THROUGHCANCELLOUS BONE;

(xii) claims benefit of pending prior U.S. Provisional PatentApplication Ser. No. 60/835,268, filed Aug. 3, 2006 by Kelly G. Ammannet al. for OPEN WEDGE OSTEOTOMY SYSTEM;

(xiii) claims benefit of pending prior U.S. Provisional PatentApplication Ser. No. 60/847,527, filed Sep. 27, 2006 by Vincent P. Novaket al. for KEYHOLE OSTEOTOMY SYSTEM; and

(xiv) claims benefit of pending prior U.S. Provisional PatentApplication Ser. No. 60/860,595, filed Nov. 22, 2006 by Kelly Ammann etal. for METHOD AND APPARATUS FOR PERFORMING AN OPEN WEDGE, HIGH TIBIALOSTEOTOMY.

The above-identified patent applications are hereby incorporated hereinby reference.

FIELD OF THE INVENTION

This invention relates to surgical methods and apparatus in general, andmore particularly to surgical methods and apparatus for performing openwedge, high tibial osteotomies of the knee.

BACKGROUND OF THE INVENTION

Osteotomies of the knee are an important technique for treating kneeosteoarthritis. In essence, knee osteotomies adjust the geometry of theknee joint to transfer weight-bearing load from arthritic portions ofthe joint to relatively unaffected portions of the joint.

Knee osteotomies are also an important technique for addressing abnormalknee geometries, e.g., due to birth defect, injury, etc.

Most knee osteotomies are designed to modify the geometry of the tibia,to adjust the manner in which the load is transferred across the kneejoint.

There are essentially two ways in which to adjust the orientation of thetibia: (i) the closed wedge technique; and (ii) the open wedgetechnique.

With the closed wedge technique, a wedge of bone is removed from theupper portion of the tibia, and then the tibia is manipulated so as toclose the resulting gap, whereby to reorient the lower portion of thetibia relative to the tibial plateau and hence adjust the manner inwhich load is transferred from the femur to the tibia.

With the open wedge technique, a cut is made into the upper portion ofthe tibia, the tibia is manipulated so as to open a wedge-like openingin the bone, and then the bone is secured in this position (e.g., byscrewing metal plates to the bone or by inserting a wedge-shaped implantinto the opening in the bone), whereby to reorient the lower portion ofthe tibia relative to the tibial plateau and hence adjust the manner inwhich load is transferred from the femur to the tibia.

While both closed wedge osteotomies and open wedge osteotomies providesubstantial benefits to the patient, they are procedurally challengingfor the surgeon. Among other things, with respect to open wedgeosteotomies, it can be difficult to create the wedge-like opening in thebone with the necessary precision and with a minimum of trauma to thesurrounding tissue (e.g., the neurological and vascular structures atthe back of the knee). Furthermore, with open wedge osteotomies, it canbe difficult to stabilize the upper and lower portions of the tibiarelative to one another and to maintain them in this position whilehealing occurs.

The present invention is directed to open wedge, high tibial osteotomiesof the knee, and is intended to provide increased precision and reducedtrauma when creating the wedge-shaped opening in the bone, and toprovide increased stability to the upper and lower portions of the tibiawhile healing occurs.

SUMMARY OF THE INVENTION

The present invention comprises a novel method and apparatus forperforming an open wedge, high tibial osteotomy. More particularly, thepresent invention comprises the provision and use of a novel method andapparatus for forming an appropriate osteotomy cut into the upperportion of the tibia, manipulating the tibia so as to open anappropriate wedge-like opening in the tibia, and then inserting anappropriate wedge-shaped implant into the wedge-like opening in thetibia, so as to stabilize the tibia with the desired orientation,whereby to reorient the lower portion of the tibia relative to thetibial plateau and hence adjust the manner in which load is transferredfrom the femur to the tibia.

In one preferred form of the present invention, there is providedapparatus for performing an open wedge, high tibial osteotomy, theapparatus comprising:

a wedge-shaped implant for disposition in a wedge-shaped opening createdin the tibia, wherein the wedge-shaped implant comprises at least twokeys, laterally offset from one another, for disposition incorresponding keyholes formed in the tibia adjacent to the wedge-shapedopening created in the tibia.

In another form of the present invention, there is provided a method forperforming an open wedge, high tibial osteotomy, the method comprising:

cutting the bone along a cutting plane, with the cut terminating at aboundary line, and forming at least two keyholes in the tibia adjacentto the cut, wherein the two keyholes are laterally offset from oneanother;

moving the bone on either side of the cut apart so as to form awedge-like opening in the bone; and

positioning a wedge-shaped implant in the wedge-shaped opening createdin the tibia, wherein the wedge-shaped implant comprises at least twokeys, laterally offset from one another, and further wherein the atleast two keys are disposed in the at least two keyholes formed in thetibia.

In another form of the present invention, there is provided apparatusfor performing an open wedge, high tibial osteotomy, the apparatuscomprising:

a wedge-shaped implant for disposition in a wedge-shaped opening createdin the tibia, wherein the wedge-shaped implant comprises at least twokeys, vertically offset from one another, for disposition incorresponding keyholes formed in the tibia adjacent to the wedge-shapedopening created in the tibia, and a shear rib, laterally offset from theat least two keys, for disposition in a corresponding shear rib keyholeformed in the tibia adjacent to the wedge-shaped opening created in thetibia.

In another form of the present invention, there is provided a method forperforming an open wedge, high tibial osteotomy, the method comprising:

cutting the bone along a cutting plane, with the cut terminating at aboundary line, and forming at least two keyholes in the tibia adjacentto the cut, wherein the two keyholes are vertically offset from oneanother, and forming a shear rib keyhole in the tibia adjacent to thecut, wherein the shear rib keyhole is laterally offset from the at leasttwo keyholes;

moving the bone on either side of the cut apart so as to form awedge-like opening in the bone; and

positioning a wedge-shaped implant in the wedge-shaped opening createdin the tibia, wherein the wedge-shaped implant comprises at least twokeys, vertically offset from one another, and a shear rib, laterallyoffset from the at least two keys, and further wherein the at least twokeys are disposed in the at least two keyholes formed in the tibia, andthe shear rib is disposed in the shear rib keyhole formed in the tibia.

In another form of the present invention, there is provided a shear ribend mill comprising:

a shaft having a distal end and a proximal end, and a relief area formedon the shaft proximal to the distal end;

a cutting edge formed on the shaft distal to relief area, and a flutecommunicating with the cutting edge and extending into relief area; and

a stop formed on the shaft, proximal to the relief area.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will bemore fully disclosed or rendered obvious by the following detaileddescription of the preferred embodiments of the invention, which is tobe considered together with the accompanying drawings wherein likenumbers refer to like parts, and further wherein:

FIGS. 1-3 are schematic views of the left leg from an anterior view,showing the formation of a wedge-like opening in the tibia for an openwedge, high tibial osteotomy, and positioning of a wedge-shaped implantinto the wedge-like opening in the tibia;

FIG. 3A is a schematic view showing selected anatomical body planes;

FIGS. 4-9 show the relevant planar surfaces in an open wedge, hightibial osteotomy conducted in accordance with the present invention fromthe anterior view and the medial view of the left leg;

FIGS. 10-30 are schematic views showing a preferred method and apparatusfor forming an appropriate osteotomy cut into the upper portion of thetibia, manipulating the tibia so as to open an appropriate wedge-likeopening in the tibia, and then inserting an appropriate wedge-shapedimplant into the wedge-like opening in the tibia;

FIGS. 31-33 are schematic views showing an alternative wedge-shapedimplant also formed in accordance with the present invention;

FIG. 34 is a schematic view showing a keyhole drill guide which may beused in conjunction with the wedge-shaped implant shown in FIGS. 31-33;

FIG. 35 is a schematic view showing another wedge-shaped implant formedin accordance with the present invention;

FIGS. 36-38 are schematic views showing still another wedge-shapedimplant formed in accordance with the present invention;

FIGS. 39-41 are schematic views show a keyhole drill guide and an endmill which may be used in conjunction with the wedge-shaped implantshown in FIGS. 36-38; and

FIGS. 42-48 are schematic views showing alternative apparatus which maybe used to form a cut in the tibia.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Overview of an OpenWedge, High Tibial Osteotomy

Looking first at FIGS. 1-3, there is shown a knee joint 5 of, forexample, the left leg from an anterior view upon which an open wedgeosteotomy is to be performed. Knee joint 5 generally comprises a tibia10 and a femur 15. In accordance with the present invention, the openwedge osteotomy is effected by first making a cut 20 (FIG. 1) into theupper tibia, and then manipulating the lower portion of the tibia so asto open a wedge-like opening 25 (FIG. 2) in the bone, with thewedge-like opening 25 being configured so as to adjust the manner inwhich load is transferred from the femur to the tibia. In this respect,it should be appreciated that a variety of methods are well known in theart for determining the degree of correction necessary to correctlyre-align the weight-bearing axis of the knee. Furthermore, cut 20 andwedge-like opening 25 may be formed in a variety of ways well known inthe art.

Among other things, the present invention provides a new and improvedmethod and apparatus for forming cut 20 and wedge-like opening 25, aswill be discussed in detail below.

Once the desired wedge-like opening 25 has been formed in tibia 10 so asto reconfigure tibia 10 to the desired geometry, the bone may be securedin position in a variety of ways well known in the art (e.g., byscrewing metal plates to the bone or by inserting a wedge-shaped implantinto the opening in the bone), whereby to adjust the manner in which theload is transferred from the femur to the tibia. By way of example, FIG.3 shows a wedge-shaped implant 27 inserted into the wedge-like opening25 formed in the tibia, whereby to stabilize the tibia in itsreconfigured geometry.

Among other things, the present invention also provides a new andimproved wedge-shaped implant, and an associated method and apparatusfor deploying the same into the wedge-shaped opening in the tibia, aswill be discussed in detail below.

Discussion of the Relevant Planar Surfaces in the Open Wedge, HighTibial Osteotomy of the Present Invention

In order to appreciate certain aspects of the present invention, it ishelpful to have a thorough understanding of the planar surfaces of thetibia that are relevant in performing the open wedge, high tibialosteotomy of the present invention. Thus, the following discussionpresents a geometric description of the planar surfaces that arerelevant to the open wedge, high tibial osteotomy of the presentinvention. For the purposes of the present discussion, it can sometimesbe helpful to make reference to selected anatomical planes, e.g., thesagittal plane 1, the coronal plane 2 (also known as the frontal plane),and the transverse plane 3 (FIG. 3A).

Looking now at FIGS. 1-4, for the purposes of the present invention, thetibial plateau 30 may be described as a horizontal (or transverse) planethat extends along the top surface of tibia 10. For reference andexample, FIG. 4 shows the left leg from an anterior view such that themedial side 6 and the lateral side 7 of the tibia 10 can be seen. Thesagittal plane 32 is also shown in FIG. 4. As seen in FIG. 5 from themedial view, tibial plateau 30 is also perpendicular to the frontal (orcoronal) plane 40. The anterior-posterior (A-P) slope is defined by ananterior-posterior (A-P) slope plane 45 that extends along the slopingtop surface of the tibia, from anterior side 12 to posterior side 10.Published research has demonstrated that the anterior-posterior (A-P)slope typically extends at an exemplary angle 13 of approximately 7° to11° to the tibial plateau 30; however, the specific angle may vary fromindividual to individual.

Looking next at FIG. 6, a medial view of the left leg, for the openwedge, high tibial osteotomy of the present invention, it is generallydesirable to stay an exemplary distance 14 of about 2 cm inferior to theA-P slope plane 45. This offset can be referred to as the A-P offsetplane 50.

As seen in FIG. 7, an anterior view of the left leg, the lateral aspectand cut depth of the cut 20 may be defined by a lateral aspect plane 55and a cut depth plane 60, with the cut depth being an exemplary distance15 of about 1 cm toward the medial side 6 from the lateral aspect plane55 of the tibia, located on the lateral side 7 of the tibia.

Looking next at FIG. 8, showing the left leg from an anterior view, theosteotomy cut plane 65 (when seen from the direct frontal view of FIG.8) is formed by a plane that is rotated away from the A-P offset plane50 through an axis which is formed by the intersection of the cut depthplane 60 and the A-P offset plane 50. The degree of rotation is selectedto be sufficient to place the entry of the osteotomy cut plane 65 at themedial neck 66 (FIG. 8) of the tibia. It should be noted that the A-Poffset plane 50 and the osteotomy cut plane 65 are “tilted” slightlyfrom anterior to posterior (but not seen in the direct frontal view ofFIG. 8), since the A-P offset plane 50 and the osteotomy cut plane 65follow the tilt of the A-P slope plane 45 (FIG. 6). The intersection ofthe A-P offset plane 50 and the cut depth plane 60 forms an axis 70that, in accordance with the present invention, defines the laterallimit of the osteotomy cut 20. In other words, axis 70 defines a linethrough the tibia, which is (i) parallel to A-P slope plane 45, and (ii)contained within osteotomy cut plane 65. Furthermore, in accordance withthe present invention, axis 70 is used to define the lateral limit ofthe osteotomy cut 20, which is to be made into the tibia.

As seen in FIG. 9, showing the left leg from an anterior view tiltedslightly superior, the direct view of the osteotomy plane is a directview in line with the osteotomy. This view is tilted downward (e.g., atan angle of approximately 7.degree.) from the direct frontal view.Again, the angle of tilt downward is equal to the A-P slope. In otherwords, with the present invention, the osteotomy cut plane 65 extendsparallel to the A-P slope plane 45 (in the anterior-to-posteriordirection, although not in the medial-to-lateral direction), andtypically slopes downward (e.g., at an angle of approximately7-11.degree.) when viewed in the anterior-to-posterior direction.Furthermore, with the present invention, the axis 70 (which defines thelateral limit to the osteotomy cut 20) is contained within the osteotomycut plane 65.

Novel Method and Apparatus for Performing the Open Wedge, High TibialOsteotomy of the Present Invention

In one preferred embodiment of the present invention, there is provideda novel osteotomy system which comprises instrumentation for use inmaking precise and repeatable osteotomy cuts for use in open wedge, hightibial osteotomies, preferably using an antero-medial approach. Thenovel osteotomy system generally comprises a positioning guide 100 (FIG.16), a slope guide 200 (FIG. 11), an apex pin 300 (FIG. 16), a keyholedrill guide 400 (FIG. 18), a posterior protector 500 (FIG. 20), and acutting guide 600 (FIG. 20), as will hereinafter be discussed in furtherdetail.

The novel osteotomy system preferably also comprises a novel openingjack 700 (FIG. 22) for opening the cut 20 in the tibia so as to form thewedge-like opening 25 in the tibia, as will also hereinafter bediscussed in further detail.

And the novel osteotomy system preferably also includes a novel implant800 (FIG. 24) for positioning in the wedge-like opening in the tibia soas to stabilize the tibia in its corrected configuration, as will alsohereinafter be discussed in further detail. Furthermore, in someinstances, it may be advantageous to use an implant trial base 830(FIGS. 27 and 28) in the course of preparing the tibia to receiveimplant 800, and in order to confirm proper fit of implant 800 in itsseat, as will also hereinafter be discussed in further detail.

Thus, with the present invention, the surgeon first determines (usingmethods well known in the art) the degree of correction necessary tocorrectly re-align the weight-bearing axis of the knee; then the surgeonuses the system to make the appropriate cut 20 into the tibia; then thesurgeon opens the bone cut to the extent required so as to form thedesired wedge-like opening 25 in the tibia; and then the surgeonstabilizes the tibia in its corrected configuration (e.g., with thenovel implant 800) while healing occurs.

In a preferred form of the invention, the novel osteotomy system isconfigured so that:

(i) the axis 70 formed at the lateral limit of the osteotomy cut 20(which forms the lateral limit of the remaining bony hinge when theosteotomy cut 20 is thereafter opened) is parallel to the A-P tibialslope;

(ii) the axis of the lateral limit of the bony hinge created by theosteotomy cut lies in a plane that is perpendicular to the frontal(i.e., coronal) plane; and

(iii) when the osteotomy cut 20 is completed and the wedge is opened,the distal (i.e., lower) tibia is rotated about the bony hinge so as tosubstantially maintain, in anatomical alignment, the A-P slope and thefrontal plane.

In a preferred form of the invention, the novel osteotomy system is alsoconfigured so that:

(iv) the osteotomy can be performed less invasively; and

(v) the osteotomy can be performed with minimum incising of soft tissuesuch as the medial collateral ligament, the lateral collateral ligament,and the hamstrings.

In a preferred form of the invention, the novel osteotomy system is alsoconfigured so that the delicate neurological and vascular tissues at theback of the knee are fully protected during the osteotomy procedure.

In one preferred form of the present invention, the novel osteotomysystem is constructed and used as follows.

A vertical incision is first made on the antero-medial portion of theknee, approximately 1 cm from the medial edge of the patellar tendon,with the incision beginning approximately 2.5-3 cm superior to theanterior tibial tubercle, and extending approximately 6-10 cm in length.

The soft tissue between the patellar tendon and the proximal surface ofthe tibia is then dissected in order to make a small tunnel-like openingbeneath the patellar tendon, just above the patellar tendon's insertionto the proximal tibia.

Looking now at FIG. 10, showing the position guide with slope guide andintroducer, an assembly comprising positioning guide 100 (FIGS. 10 and16), slope guide 200 (FIGS. 10 and 11) and an introducer 105 (FIGS. 10and 11) is advanced to the surgical site. FIG. 10 shows the tibia 10oriented such that the left leg is seen with the medial side 6, lateralside 7, posterior side 11, and anterior side 12 as shown. Preferably,the assembly of positioning guide 100, slope guide 200, and introducer105 is pre-assembled prior to opening the skin. This assembly isassembled by first mounting slope guide 200 to positioning guide 100,and then mounting introducer 105 to both slope guide 200 and positioningguide 100 by using a screw 115 (FIG. 10) which passes through slopeguide 200 and is received in a threaded bore 120 (FIG. 16) formed inpositioning guide 100.

In one preferred form of the invention, slope guide 200 may comprise twoseparate elements which are secured together, e.g., a base 210 and aguide element 215 which are connected together by pins 205, with base210 being formed out of a radio-translucent material (e.g., plastic) andguide element 215 being formed out of a radio-opaque material (e.g.,stainless steel), whereby guide element 215 will be visible underfluoroscopy and base 210 will be effectively invisible underfluoroscopy, as will hereinafter be discussed. In one preferred form ofthe invention, introducer 105 may comprise an arm 125 and a handle 130.Arm 125 and handle 130 may be formed as two separate elements securedtogether, or arm 125 and handle 130 may be formed as a singularconstruction.

Next, the foregoing assembly is maneuvered so that a tibial tuberclelocating tab 135 (FIGS. 10 and 16) of positioning guide 100 is insertedbetween the patellar tendon (not shown) and the tibia, and so thattibial tubercle locating tab 135 is set against the superior margin ofthe tibial tubercle. In this way, the tibial tubercle provides a roughalignment guide for aligning positioning guide 100 with the tibia. Ifdesired, the underside of tibial tubercle locating tab 135 may includeserrations 138, ridges, ribs, etc. (FIGS. 11D and 11E) so as tofacilitate stabilization of tibial tubercle locating tab 135 (and hencethe instrumentation) against the tibia.

Using a lateral fluoroscope view, taken from the medial side at thelevel of the tibial plateau, the assembly is then aligned so that theunderside surface 220 (FIG. 11) of guide element 215 of slope guide 200is aligned with the top of the medial condyle 75 of the tibia.Alternatively, if the surgeon prefers to shift the osteotomy slightlydistally on the tibia, the top edge 225 of guide element 215 of slopeguide 200 can be aligned with medial condyle 75, thereby offsetting theosteotomy by a fixed distance distally (e.g., 3 mm).

By forming the guide element 215 of slope guide 200 out of aradio-opaque material and by forming the base 210 of slope guide 200 outof a radio-translucent material, base 210 will be effectively invisibleunder fluoroscopy and guide element 215 will stand out in clear reliefagainst the bone.

It should be noted that guide element 215 of slope guide 200 ispreferably formed with a “Z shape” (FIGS. 10 and 11A) to provideadditional functionality. More particularly, by forming guide element215 with a “Z shape,” several significant advantages are obtained.First, this construction permits guide element 215 to wrap around theperimeter of the tibia. Second, the “Z shape” of guide element 215 alsooperates to indicate if the slope guide is not vertically aligned withthe level of the fluoroscope. More particularly, if, from a lateralview, the slope guide 200 is not vertically aligned with the level ofthe fluoroscope, the “Z shape” of guide element 215 will appear as ajagged or zig-zag shape on the fluoroscope (FIG. 11B). However, if guideelement 215 is vertically aligned with the level of the fluoroscope,then the guide element will appear as a straight line on the fluoroscope(FIGS. 11 and 11C). This vertical alignment is important, since itenables alignment of slope guide 200 (and hence positioning guide 100)with the medial condyle, i.e., with the A-P slope plane.

If desired, and looking now at FIG. 11D, showing the position guide 100,slope guide 200, and introducer 105, 11E, showing the tibia tuberclelocating tab 135 and serrations 138, and 11F, showing the slope guide200 aligned with the anterior-posterior slope, it is also possible toprovide guide element 215 of slope guide 200 with an “L shape”configuration, rather than the “Z shape” configuration discussed above.Again, this construction provides several benefits. First, the “L shape”configuration permits guide element 215 to wrap around the perimeter ofthe tibia. Second, the “L shape” of guide element 215 also operates toindicate if the slope guide is not vertically aligned with the level ofthe fluoroscope. More particularly, if slope guide 200 is not verticallyaligned with the level of the fluoroscope, the “L shape” of guideelement 215 will appear as an “L shape” on the fluoroscope. However, ifguide element 215 is vertically aligned with the level of thefluoroscope, then the guide element will appear as a straight line onthe fluoroscope. Again, this vertical alignment is important, since itenables alignment of slope guide 200 (and hence positioning guide 100)with the medial condyle, i.e., with the A-P slope plane.

The assembly is then maneuvered so that the medial locating pin 140(FIGS. 10, 11 and 16), preferably formed as a pin although it could alsobe formed as a tab, fin, etc., is located against the medial aspect 80(FIG. 16) of the tibia. As further adjustments in position are made,medial locating pin 140 is held in contact with the medial aspect of thetibia, thereby ensuring proper alignment of the instrumentation. Mediallocating pin 140 references the medial aspect of the tibia, thus settingthe distance from the medial aspect of the tibia to the apex pin 300(FIG. 10), as will hereinafter be discussed. This reference distance isused in conjunction with the sizing of the osteotomy implant 27 (FIG. 3)so as to ensure a proper tibial reconstruction, e.g., the distance fromthe medial aspect of the tibia to the center of apex pin 300 maycorrespond to the distance from the medial aspect of the implant to thevertex of the wedge angle of the implant.

In another form of the invention, the reference distance may be thedistance from the medial aspect of the tibia to a neutral axis ofrotation in the bony hinge, which could be estimated by calculation. Inthis case, the distance from the medial aspect of the tibia to theneutral axis of the bony hinge may correspond to the distance from themedial aspect of the implant to the vertex of the wedge angle of theimplant.

The assembly is then rotated around the primary tibial anatomical axis,by sliding introducer handle 130 in a side-to-side motion, such that theinstrumentation is aligned perpendicular to the frontal (coronal) plane,i.e., so that introducer 105 and apex pin 300 (see below) will extendparallel to the sagittal plane of the patient. To this end, slope guide200 is provided with a ball 230 and a groove 235 (FIG. 10). With thefluoroscope arranged so that it is set in the lateral mode, with theimage being taken from the medial side at the level of the tibialplateau (see FIG. 11), the assembly is maneuvered until ball 230 iscentered in groove 235 (FIG. 11) this creates the ball and groovealignment sight 240. When this occurs, the system is aligned with thesagittal plane (i.e., positioning guide 100 is disposed so that apex pin300 will extend perpendicular to the frontal plane, as will hereinafterbe discussed).

Thus, when slope guide 200 is aligned with the medial condyle 75, andwhen ball 230 is aligned with groove 235, the system is aligned with (i)the A-P slope, and (ii) the sagittal plane. In other words, when slopeguide 200 is aligned with medial condyle 75, and when ball 230 isaligned with groove 235, the instrumentation is positioned so that apexpin 300 (see below) is aligned with both the A-P slope and the sagittalplane, as will hereinafter be discussed.

With all of the previous adjustments established, the positions of (i)tibial tubercle locating tab 135, (ii) slope guide 200, (iii) mediallocating pin 140, and (iv) the ball and groove sights 230, 235 areverified. With all positions confirmed, the frontal pin 145 (FIG. 16)and the antero-medial (A-M) pin 150 (FIG. 16) are inserted throughpositioning guide 100 and into the tibia. This secures positioning guide100 to the tibia with the desired alignment.

Next, apex pin 300 is inserted through positioning guide 100 and intothe tibia. An apex aimer 155 (FIGS. 14 and 16) serves to guide apex pin300 into the tibia with the proper orientation, i.e., so that apex pin300 is positioned along the axis 70 which is located at the laterallimit of the intended osteotomy cut, with apex pin 300 extendingparallel to the A-P slope and perpendicular to the coronal plane, andbeing coplanar with cutting plane 65. As a result, apex pin 300 canserve as the lateral stop for the osteotomy saw, whereby to clearlydefine the perimeter of the bony hinge, as will hereinafter bediscussed. Apex pin 300 may be tapped or drilled into virgin bone, or itmay be received in a pre-drilled hole (e.g., formed using apex aimer 155and a standard surgical drill). A thumbscrew 160 (FIG. 16) may be usedto secure apex pin 300 to positioning guide 100.

Apex pin 300 may be generally cylindrical in shape and, if desired, apexpin 300 may be provided with a rounded, or “bullet-shaped”, nose 303, orother tapered end configuration, so as to facilitate deployment into thetibia (FIG. 11G).

Furthermore, if desired, apex pin 300 may have a flat 305 (FIGS. 12 and13) formed thereon to promote a complete cut-through of the osteotomycut 20. Where apex pin 300 is provided with a distinct flat 305, it ispreferably provided with a counterpart flat 310 (FIGS. 12 and 13), suchthat when apex pin 300 is positioned within the tibia and thumbscrew 160is tightened against flat 310, the aforementioned flat 305 will bealigned with the osteotomy cut, whereby to ensure that the osteotomyblade cuts completely through the bone to reach the apex pin. See FIG.13.

In another version of this construction (not shown), the flats 305, 310may be diametrically opposed to one another, with thumbscrew 160 alsobeing aligned with the osteotomy cut, whereby to make insertion of apexpin 300 less prone to error.

And in another embodiment of the present invention, apex pin 300 may benecked down to a smaller diameter in the area of the osteotomy. As aresult of this construction, a slight relief area exists to accommodatethe saw blade so as to help promote a complete cut-through, but does notrequire any specific orientation of the apex pin with respect to theosteotomy plane, as is the case where the apex pin is formed withdistinct flats.

And in another version of the present invention, apex aimer 155 may beused with an optional guide sleeve 161 (FIG. 14) and a small-diameterguide pin 165 in order to first check the position of the small-diameterguide pin 165 relative to the desired axis for the apex pin, beforethereafter deploying the larger-diameter apex pin 300. In this respect,it will be appreciated that repositioning a misdirected small-diameterguide pin 165 is easier and less traumatic to the host bone thanrepositioning a misdirected larger-diameter apex pin 300.

As seen in FIG. 15, tibial tubercle locating tab 135 is preferably sizedso that it also functions as an anterior protector, by providing aprotective shield between the oscillating saw blade (to be used later inthe procedure to form the osteotomy cut 20) and the anterior soft tissuestructures, e.g., the patellar tendon. Thus, tibial tubercle locatingtab 135 also functions as a patellar tendon protector.

By virtue of the foregoing, it will be seen that apex pin 300 ispositioned in the patient's tibia so that the apex pin extends (i)parallel to the A-P slope of the tibia, and (ii) parallel to thesagittal plane of the patient. As a result, when the osteotomy cut 20 issubsequently formed in the bone (see below) by cutting along theosteotomy cut plane until the apex pin is engaged by the bone saw, sothat the perimeter of the bony hinge is defined by the location of theapex pin, the bony hinge will extend (i) parallel to the A-P slope ofthe tibia, and (ii) parallel to the sagittal plane of the patient. Byensuring that apex pin 300 is set in the aforementioned fashion, andhence ensuring that the bony hinge is so created, the finalconfiguration of the tibia can be properly regulated when the bone cutis thereafter opened to form the open wedge osteotomy.

As shown in FIG. 16, once apex pin 300 has been properly positioned onthe tibia 10, slope guide 200 and introducer 105 are removed, leavingpositioning guide 100 properly aligned on, and secured to, the tibia,with apex pin 300 extending parallel to the A-P slope and parallel tothe sagittal plane of the patient. See FIG. 16.

The size of positioning guide 100 and the associated instrumentation areused to prepare the osteotomy to fit a particular implant sizing ofsmall, medium or large. More particularly, the medial locating pin 140,the size of positioning guide 100, and apex pin 300 all combine toimplement an implant-sizing scheme of small, medium or large. As seen inFIG. 17, medial locating pin 140, positioning guide 100, and apex pin300 combine to provide a known, fixed distance from the medial aspect ofthe tibia to the apex pin. The size of the planned osteotomy is thenset, allowing a specifically-sized implant (e.g., small, medium orlarge) to nominally fit between the medial aspect of the tibia and theapex pin.

In the embodiment shown in FIG. 17, the position guide 100 possesses afixed distance for sizing 180 from the apex pin 300 to the mediallocating pin 140. In this embodiment, this creates a known lateraloffset 175 between medial locating pin 140 and the entry point of theosteotomy cut 20. The implant size is reduced slightly to factor in thisoffset distance to yield a proper fit.

In a more preferred construction, and looking now at FIG. 17A, mediallocating pin 140 is substantially aligned with the entry point of theplanned osteotomy, which eliminates the lateral offset 175.

Looking next at FIG. 18, keyhole drill guide 400 is then attached topositioning guide 100 by passing keyhole drill guide 400 over frontalpin 145 and apex aimer 155. Keyhole drill guide 400 is then secured inthis position with thumbscrew 405. At this point, a distal pin 410 isinserted through keyhole drill guide 400 and into the tibia. Distal pin410 further secures the instrumentation to the tibia. Next, a surfacelocator pin 415 is inserted through keyhole drill guide 400. Surfacelocator pin 415 slides through keyhole drill guide 400 until the distaltip of surface locator pin 415 contacts the surface of the tibia. Forthe purposes of the present invention, this surface may be referred toas the “antero-medial surface” or the “A-M surface,” which is theanatomical surface of the tibia corresponding to the antero-medialapproach of the osteotomy. When surface locator pin 415 contacts the A-Msurface, the surface locator pin can act as an indicator as to thelocation of the A-M surface. This information can then be used to setthe depth of the keyholes, which are to be formed in the tibia (seebelow) for an improved implant fit.

Next, an end mill 420 is inserted into the distal hole 425 (i.e., thebottom hole 425) of keyhole drill guide 400 and drilled until a stopflange 430 on end mill 420 contacts the proximal end of surface locatorpin 415, whereby to form the distal keyhole 85 (FIG. 21) in the tibia.The drilling procedure is then repeated for the proximal hole 435 (i.e.,the top hole 435), whereby to form the proximal keyhole 90 (FIG. 21) inthe tibia. Thus, keyholes 85 and 90 are formed so that one keyhole(i.e., proximal keyhole 90) sits above the other keyhole (i.e., distalkeyhole 85). While it is possible to drill the proximal keyhole beforethe distal keyhole, it is generally preferable to drill the distalkeyhole first. This is because drilling the distal keyhole before theproximal keyhole reduces the possibility that the sloping nature of thebone will cause a later-drilled keyhole to slip into an earlier-drilledkeyhole. It should be appreciated that keyhole drill guide 400 isconfigured so that distal hole 425 and proximal hole 435 will overlapthe osteotomy cutting plane 65 to some extent (FIG. 21), so that whenosteotomy cut 20 is thereafter formed and the tibia subsequently openedso as to create the wedge-like opening 25, distal keyhole 85 andproximal keyhole 90 will overlap, and communicate with, the wedge-likeopening 25 (FIG. 29).

Once the two-implant keyholes have been drilled into the tibia, end mill420 is removed, thumbscrew 405 is loosened, and then keyhole drill guide400 is removed.

Next, and looking now at FIG. 19, posterior protector 500 is attached toan introducer 505 with a thumbscrew 510, and handle 535. Posteriorprotector 500 preferably comprises a far tip 515 and a curved portion520. Far tip 515 is preferably formed out of a flexible material tofacilitate passage of the posterior protector along the surface of theposterior cortex and beneath overlying soft tissue. Curved portion 520comprises a relatively stiff material, which provides support for fartip 515. Far tip 515 of posterior protector 500 is inserted into theincision and worked along the posterior cortex of the tibia until fartip 515 of posterior protector 500 substantially crosses the axis of,and in some cases actually engages, apex pin 300 (FIG. 21). Onceposterior protector 500 has been properly deployed, the thumbscrew 510is unscrewed, and introducer handle 505 is removed, leaving posteriorprotector 500 extending along the posterior cortex of the tibia,interposed between the tibia and the delicate neurological and vascularstructures located at the back of the knee.

Looking next at FIGS. 20 and 21, cutting guide 600 is then attached topositioning guide 100 and secured in place using cutting guidethumbscrew 605. Cutting guide 600 comprises alignment features shown inFIGS. 20 and 21. These include alignment rods 610 that extend from thecutting guide into the pre-drilled keyholes 85, 90 to assist withcutting alignment. More particularly, alignment rods 610 ensure properalignment between cutting guide 600, its cutting slot 615 (FIGS. 20 and21) and the pre-drilled keyholes 85, 90 previously formed in the tibiawith end mill 420 and, ultimately, ensure the desired fit between theimplant and the tibia.

Then, posterior protector 500 is attached to cutting guide 600 usingthumbscrew 620 (FIG. 20).

At this point, the instrumentation is ready to form the osteotomy cut,with cutting slot 615 of cutting guide 600 properly aligned with theosteotomy cut plane, apex pin 300 properly positioned at the far(lateral) limit of the osteotomy cut, tibial tubercle locating tab 135forming a protective shield for the patellar tendon, and with posteriorprotector 500 forming a protective shield for the vascular andneurological structures at the back of the knee. In this respect, itshould be appreciated that cutting guide 600 is sized and shaped, andcutting slot 615 is positioned, so that, in addition to being alignedwith the apex pin 300, the entry point of the cutting plane into thetibia is located at an appropriate location on the tibia's medial neck66.

Next, a saw blade 625 (attached to an oscillating saw, not shown) isinserted into cutting slot 615 of cutting guide 600. The osteotomy cutis then made by plunging the oscillating saw blade through cutting slot615 and into the bone (FIG. 20). The saw blade is used to cut completelythrough the medial and posterior cortices. The saw is operated until sawblade 625 contacts posterior protector 500 and apex pin 300. As the sawblade cuts through the tibia, it is constrained by cutting slot 615,apex pin 300 and posterior protector 500, so that the saw blade may onlycut bone along the osteotomy plane, up to (but not beyond) the desiredlocation of the bony hinge, and does not cut soft tissue. Duringcutting, tibial tubercle locating tab 135 also ensures that the sawblade will not inadvertently cut the patellar tendon.

After saw blade 625 forms the desired osteotomy cut 20 along the cuttingplane, the saw blade is removed, and a hand osteotome (not shown) of thesort well know in the art is inserted through cutting slot 615 and intothe osteotomy cut 20, and then the cut is completed through theposterior cortical bone near apex pin 300 and posterior protector 500.Then the hand osteotome is removed.

At this point the osteotomy cut 20 has been completed, with theosteotomy cut terminating on the lateral side at apex pin 300, so thatthe bony hinge is properly positioned at the desired location, i.e.,parallel to the A-P slope and perpendicular to the coronal plane.

Next, thumbscrew 620 is loosened and posterior protector 500 removed.Then thumbscrew 605 is loosened and cutting guide 600 is removed.

At this point, the desired osteotomy cut 20 has been formed in thetibia, with keyholes 85 and 90 formed below and above, respectively, theosteotomy cut.

In order to complete the procedure, the bone must now be opened so as toreconfigure the tibia to the desired geometry, and then the tibiastabilized with the desired configuration, e.g., by inserting awedge-shaped implant 27 into wedge-like opening 25.

Looking next at FIG. 22, opening jack 700 is assembled onto theinstrumentation by receiving frontal pin 145 in a hole 705 formed injack arm 710, by receiving apex aimer 155 in another hole 715 formed injack arm 710 and jack arm 725, and by receiving distal pin 410 in a slot720 formed in jack arm 725. Opening jack 700 is secured to positioningguide 100 with a thumbscrew 730.

As is shown in FIG. 23, once opening jack 700 is in place, the jack isopened by rotating jack screw 735. This causes jack arm 725 to pivotabout apex aimer 155 to open the jack and thereby open the desiredwedge-like opening 25 in the tibia. Preferably, the patient's lower legis manipulated as jack screw 735 is turned to assist in opening of thebone. As the wedge-like opening 25 is created in the bone, the tibiawill be reoriented in a highly controlled manner, due to the fact thatthe bony hinge will be precisely positioned at axis 70 using apex pin300, i.e., the bony hinge will extend parallel to the A-P slope andparallel to the sagittal plane. Furthermore, as the wedge-like opening25 is created in the bone, the risk of bone cracking will be minimized,due to the fact that apex pin 300 forms an oversized hole 95 (FIGS. 23Aand 27) at the lateral end of the bone cut, i.e., “oversized” relativeto the thickness of the osteotomy cut, whereby to reduce the occurrenceof stress risers and the like as the bone is opened.

The surgeon uses opening jack 700 to open the bone to the extentnecessary to correctly re-align the weight-bearing axis of the knee.

Then, with opening jack 700 still in place, an implant is positioned inthe wedge-like opening 25.

If desired, the implant may be a “generic” implant such as the implant27 shown in FIG. 3.

More preferably, however, and looking now at FIG. 24, there is shown awedge-shaped implant 800 formed in accordance with the presentinvention. Wedge-shaped implant 800 is characterized by a wedge-likeside profile configured to match the geometry of the wedge-like opening25 (i.e., to match the prescribed correction angle of the open wedge,high tibial osteotomy). Preferably, wedge-shaped implant 800 is alsoformed so as to have a U-shaped top profile, such that it can form abarrier about the perimeter of the wedge-like opening 25, whereby tocontain graft material (e.g., bone paste, bone cement, etc.) which maybe positioned within the interior of the wedge-like opening 25. In onepreferred form of the present invention, wedge-shaped implant 800 isformed so as to have an asymmetric configuration when viewed in a topview, so as to mate with the geometry of the tibia when the implant ispositioned using an antero-medial approach. Wedge-shaped implant 800 issized to match the known distance from the medial aspect of the tibia tothe axis of the bony hinge, which is set by the position of apex pin300. Wedge-shaped implant 800 may be formed out of absorbable materialor non-absorbable material, as desired.

In one preferred form of the invention, and looking now at FIGS. 25 and26, implant 800 preferably comprises a three-part assembly, comprisingposterior graft containment arm (GCA) 805, a base 810 and an anteriorgraft containment arm (GCA) 815. The individual components of implant800 may each be formed out of absorbable material and/or non-absorbablematerial, as desired. Furthermore, where one or more of the implantcomponents is formed out of an absorbable material, the absorptioncharacteristics of the material may vary as desired. By way of examplebut not limitation, base 810 may be formed out of a relativelyslowly-absorbing material, while posterior graft containment arm (GCA)805 and anterior graft containment arm (GCA) 815 may be formed out of arelatively faster-absorbing material. Base 810 preferably comprises apair of keys 820, 825. Further, the keys 820, 825 may be split to allowfor expansion of the key 838.

In one preferred form of the invention, implant 800 is formed so thatposterior graft containment arm (GCA) 805 has a generally wedge-shapedprofile including an engagement seat 826 comprising an alignment post827, and an introducer hole 828 opening on the antero-medial side of thecomponent for engagement with introducer 845 (see below). Astrengthening rib 829 is preferably provided as shown. Additionally,raised points or dimples 831 may be provided to help fix posterior graftcontainment arm (GCA) 805 to the bone. An alignment tab 832 is providedfor extension into upper keyhole 90 (FIG. 29) when posterior graftcontainment arm (GCA) 805 is positioned in the wedge-shaped opening 25.

And in one preferred form of the invention, base 805 is formed so thatits keys 820, 825 each includes a bore 833, 834, respectively, with thekeys being slotted longitudinally so as to permit expansion of the keyswhen screws 865 are thereafter deployed in the bores, whereby to helplock the implant against the hard cortical bone of the tibia. Externalribs 836 may be provided on the outer surfaces of keys 820, 825 to helpfix keys 820, 825 in keyholes 85, 90, respectively, when keys 820, 825are expanded, as will hereafter be discussed in further detail. Externalribs 836 may extend longitudinally or circumferentially. Keys 820, 825protrude from the upper and lower surfaces of base implant 810, andaccommodate shear loads, which may be imposed across the implant.Furthermore, expansion of keys 820, 825 creates an interference fit withthe cortical bone of the tibia, and can help support tensile loads,which may be imposed across the implant. An alignment mechanism (notshown) is provided for mating with alignment post 827 of posterior graftcontainment arm (GCA) 805.

The bores 833, 834 may be axially aligned with the longitudinal axes ofkeys 820, 825, respectively. Alternatively, the bores 833, 834 may bearranged so that they diverge from one another, downwardly and upwardly,respectively, to direct screws 865 deeper into the adjacent portions ofthe tibia.

Anterior graft containment arm (GCA) 815 also comprises a generallywedge-shaped profile, and an alignment tab 837 is provided for extensioninto lower keyhole 85 when GCA 815 is positioned in the wedge-shapedopening 25.

Implant 800 is preferably assembled in situ.

In some instances, it may be advantageous to use an implant trial base830 (FIGS. 27 and 28) in the course of preparing the tibia to receiveimplant 800, and in order to confirm proper fit of implant 800 in itsseat.

More particularly, a pre-assembled assembly comprising posterior graftcontainment arm (GCA) 805, an implant trial base 830 and two guidesleeves 835, 840 are first inserted into wedge-like opening 25 in thebone using an introducer 845. See FIGS. 27 and 28.

Next, a drill sleeve 850 and a drill 855 are inserted into guide sleeve840 (FIG. 27). An upper hole is drilled into the tibia with the drill.The drilling procedure is then repeated for guide sleeve 835 to create alower hole. Then drill sleeve 850 and drill 855 are removed from thesurgical site. Next, a tap 860 is inserted into guide sleeve 840 and theupper hole is tapped. See FIG. 28. Then the tap is inserted into guidesleeve 835 and the lower hole is tapped. Then tap 860 is removed fromthe surgical site.

Next, posterior graft containment arm (GCA) 805 is released fromintroducer 845, and then introducer 845 and implant trial base 830 areremoved. Posterior graft containment arm (GCA) 805 remains in wedge-likeopening 25.

Then, if desired, graft material is packed into the osteotomy opening.

Next, anterior graft containment arm (GCA) 815 is placed into theosteotomy opening and aligned with the prepared implant holes. See FIG.29. If necessary, jack screw 735 is rotated as needed to facilitateinsertion of anterior GCA 815. At this point in the procedure, posteriorgraft containment arm (GCA) 805 and anterior graft containment arm (GCA)815 are positioned in wedge-like opening 25.

Then implant base 810 is inserted into the prepared osteotomy, with keys820 and 825 seated in tibial holes 85 and 90, respectively, and withbase 810 capturing posterior graft containment arm (GCA) 805 andanterior graft containment arm (GCA) 815 against the bony hinge. Keys820 and 825, seating in keyholes 85 and 90, help ensure a precise fit ofthe implant to the bone. As this is done, jack screw 735 is adjusted asnecessary to facilitate insertion of the base into the osteotomy. Thenjack screw 735 is tightened slightly so as to ensure that the implantcomponents are fully seated into the osteotomy wedge, with at leastimplant base 810, and preferably also posterior graft containment arm(GCA) 805 and anterior graft containment arm (GCA) 815, providing loadbearing support to the tibia. Next, fixation screws 865 are insertedthrough keys 820 and 825 in base 810 and into the tapped holes in thetibia, and then tightened into place. As this occurs, fixation screws865 expand keys 820, 825 to lock keys 820, 825 to the adjacent corticalbone, and fixation screws 865 extend into the tibia, to further lock theimplant in position. See FIG. 30. Finally, opening jack 700, positioningguide 100, apex pin 300, distal pin 410, frontal pin 145, and A-M pin150 are removed from the surgical site, and the incision closed.

Providing implant 800 with two graft containment arms, e.g., posteriorgraft containment arm (GCA) 805 and anterior graft containment arm (GCA)815, is frequently preferred. However, in some circumstances, it may bedesirable to omit one or both of posterior graft containment arm (GCA)805 and anterior graft containment arm (GCA) 815. Thus, in one preferredform of the invention, implant 800 comprises only base 810 and omitsboth posterior graft containment arm (GCA) 805 and anterior graftcontainment arm (GCA) 815.

Providing implant 800 with a pair of keys 820, 825 is generallypreferred. However, in some circumstances, it may be desirable to omitone or the other of keys 820, 825. Furthermore, in other circumstances,it may be desirable to provide more than two keys, e.g., to providethree keys.

Furthermore, each of the keys 820, 825 may include more than one bore833, 834. Thus, for example, a key may include two bores, one angledleftward to direct a fixation screw leftward into the tibia to the leftof the key, and/or one angled rightward to direct a fixation screwrightward into the tibia to the right of the key.

The use of apex pin 300 is significant for a number of reasons:

(1) the oversized, circular diameter hole 95 formed in the tibia by apexpin 300, which forms the limit of bone cut 20, effectively displaces thestress forces created at the edge of the bony hinge when the cut isopened to form the wedge-like opening 25, thereby adding significantlyto the effective strength of the bony hinge;

(2) by using apex pin 300 to control the length of bone cut 20 (asmeasured from the medial aspect of the tibia to the apex pin), the seatfor the implant is always of known size, thereby simplifying properfitting of the implant to its seat in the bone, and also reducing theinventory of different-sized implants which must be on hand during thesurgery;

(3) with apex pin 300 in place, bone resecting tools can be used withincreased confidence, without fear of inadvertently cutting into, oreven through, the bony hinge; and

(4) since apex pin 300 controls the depth of bone cut 20, the implantcan be reliably manufactured to appropriately address the requireddegree of correction needed to effect knee realignment (e.g., a 4 degreeimplant slope will always provide a 4 degree angle of correction).

Furthermore, the provision of (i) apex pin 300, posterior protector 500and tibial tubercle locating tab 135 creates a “protection zone”, and(ii) cutting guide 600 creates a closely constrained cutting path forsaw blade 625, thereby together ensuring that only the desired portionof the bone is cut. Among other things, the provision of posteriorprotector 500 ensures that the delicate neurological and vasculartissues at the back of the knee are protected during cutting of thetibia.

The provision of keyholes 85, 90 in the tibia, and the provision of keys820, 825 in the implant, is significant inasmuch as they provideimproved stabilization of the implant, particularly against rotationaland shearing forces. This is particularly true inasmuch as keyholes 85,90 extend through the hard cortical bone at the periphery of the tibia.

Additional Constructions

Looking next at FIGS. 31-33, there is shown an implant 800A also formedin accordance with the present invention. Implant 800A is generallysimilar to the implant 800 disclosed above, except that implant 800A hasits keys disposed in a “side-by-side” disposition, rather than the“over-under” disposition of implant 800, as will hereinafter bediscussed in further detail. Furthermore, implant 800A also provides analternative approach for joining the posterior graft containment arm(GCA) to the base, and an alternative approach for joining the anteriorgraft containment arm (GCA) to the base, as will hereinafter also bediscussed in further detail.

More particularly, and still looking now at FIGS. 31-33, implant 800Acomprises a posterior graft containment arm (GCA) 805A, a base 810A andan anterior graft containment arm (GCA) 815A. Base 810A preferablycomprises a pair of keys 820A, 825A. Keys 820A, 825A are laterallydisplaced along the width of base 810A, in a “side-by-side”configuration. This is in contrast to the construction of implant 800,which uses an “over-under” configuration for its keys 820, 825 (FIG.24). Among other things, it has been found that the “side-by-side”configuration provides, at the base of the implant, excellentload-bearing characteristics and substantial resistance to rotationaland shear forces.

Posterior graft containment arm (GCA) 805A includes a tab 870A, and base810A includes a groove 873A, whereby posterior graft containment arm(GCA) 805A can mate with base 810A. A screw 875A is used to secure tab870A in groove 873A, and hence posterior graft containment arm (GCA) 805to base 810. Anterior graft containment arm (GCA) 815A includes a flange878A, and implant base 810A includes a recess 881A, whereby anteriorgraft containment arm (GCA) 815A can mate with base 810A. Another screw875A is used to secure flange 878A in recess 881A, and hence anteriorgraft containment arm (GCA) 815 to base 810. As is shown in FIG. 33, thetab 870A and groove 873A can be configured to interlock at theirinterface.

Posterior graft containment arm (GCA) 805A, and/or anterior graftcontainment arm (GCA) 815A, may include raised points or dimples 831A.

Keys 820A, 825A each include a bore 833A, 834A, respectively. Bores833A, 834A receive fixation screws 865A for fixing implant 800A to thetibia. Bores 833A, 834A preferably diverge from the longitudinal axes ofkeys 820A, 825A, respectively, to direct fixation screws 865A downwardlyor upwardly into the adjacent portions of the tibia. Keys 820A, 825A mayalso include external ribs 836A. External ribs 836A may extendlongitudinally or circumferentially. Keys 820A, 825A may also be slotted(i.e., in a manner analogous to the slots provided in keys 820, 825 ofimplant 800), whereby to permit keys 820A, 825A to expand when fixationscrews 865A are received in bores 833A, 834A.

In order to provide appropriate keyholes 85A, 90A (FIG. 31) forreceiving keys 820A, 825A, a keyhole drill guide 400A (also sometimesreferred to as a “keystone drill template”) may be used (FIG. 34).Keyhole drill guide 400A is generally similar to the keyhole drill guide400 disclosed above, except that keyhole drill guide 400A has its twoguide holes 425A, 435A disposed in a “side-by-side” disposition, ratherthan the “over-under” disposition of the two guide holes 425, 435 ofdrill guide 400.

Implant 800A (and drill guide 400A) may be used in an open wedge, hightibial osteotomy in a manner, which is generally similar to thatpreviously described with respect to implant 800 (and drill guide 400).

Providing implant 800A with two graft containment arms, e.g., posteriorgraft containment arm (GCA) 805A and anterior graft containment arm(GCA) 815A, is frequently preferred. However, in some circumstances, itmay be desirable to omit one or both of posterior graft containment arm(GCA) 805A and anterior graft containment arm (GCA) 815A. Thus, in onepreferred form of the invention, implant 800A comprises only base 810Aand omits both posterior graft containment arm (GCA) 805A and anteriorgraft containment arm (GCA) 815A.

Providing implant 800A with a pair of keys 820A, 825A is generallypreferred. However, in some circumstances, it may be desirable to omitone or the other of keys 820A, 825A. Furthermore, in othercircumstances, it may be desirable to provide more than two keys, e.g.,to provide three keys.

Furthermore, each of the keys 820A, 825A may include more than one bore833A, 834A. Thus, for example, a key may include two bores, one angledupwardly to direct a fixation screw upwardly into the tibia above thekey, and/or one angled downwardly to direct a fixation screw downwardlyinto the tibia below the key.

Looking next at FIG. 35, there is shown another implant 800B also formedin accordance with the present invention. Implant 800B is generallysimilar to the implant 800A disclosed above, except that implant 800Bprovides an alternative approach for joining the anterior graftcontainment arm (GCA) to the implant base using sliding faces and afastener, among other things.

More particularly, and still looking now at FIG. 35, implant 800Bcomprises a posterior graft containment arm (GCA) 805B, a base 810B andan anterior graft containment arm (GCA) 815B. Base 810B preferablycomprises a pair of keys 820B, 825B. Keys 820B, 825B are laterallydisplaced along the width of base 810B, in a “side-by-side”configuration. Again, this is in contrast to the construction of implant800, which uses an “over-under” configuration for its keys 820, 825(FIG. 24).

Posterior graft containment arm (GCA) 805B includes a tab 870B, and base810B includes a groove 873B, whereby posterior graft containment arm(GCA) 805B can mate with base 810B. Anterior graft containment arm (GCA)815A includes a slide face 883B, and implant base 810B includes anopposing slide face 885B, whereby anterior graft containment arm (GCA)815B can mate with base 810B. A bridge-type fastener 888B is used tosecure anterior graft containment arm (GCA) 815B in position, with armslide face 883B engaging base slide face 885B, after the implant ispositioned within positioned within the wedge-like opening 25.

Posterior graft containment arm (GCA) 805B, and/or anterior graftcontainment arm (GCA) 815B, may include raised points or dimples 831B.

Keys 820B, 825B each include a bore 833B, 834B, respectively. Bores833B, 834B receive fixation screws 865B for fixing implant 800B to thetibia. Bores 833B, 834B preferably diverge from the longitudinal axes ofkeys 820B, 825B, respectively, to direct fixation screws 865B downwardlyor upwardly into the adjacent portions of the tibia. Keys 820B, 825B mayalso include external ribs 836B. External ribs 836B may extendlongitudinally or circumferentially. Keys 820B, 825B may also be slotted(i.e., in a manner analogous to the slots provided in keys 820, 825 ofimplant 800), whereby to permit keys 820B, 825B to expand when fixationscrews 865B are received in bores 833B, 834B.

Implant 800B may be used in an open wedge, high tibial osteotomy in amanner that is generally similar to that previously described withrespect to implant 800.

Providing implant 800B with two graft containment arms, e.g., posteriorgraft containment arm (GCA) 805B and anterior graft containment arm(GCA) 815B, is frequently preferred. However, in some circumstances, itmay be desirable to omit one or both of posterior graft containment arm(GCA) 805B and anterior graft containment arm (GCA) 815B. Thus, in onepreferred form of the invention, implant 800B comprises only base 810Band omits both posterior graft containment arm (GCA) 805B and anteriorgraft containment arm (GCA) 815B.

Providing implant 800B with a pair of keys 820B, 825B is generallypreferred. However, in some circumstances, it may be desirable to omitone or the other of keys 820B, 825B. Furthermore, in othercircumstances, it may be desirable to provide more than two keys, e.g.,to provide three keys.

Furthermore, each of the keys 820B, 825B may include more than one bore833B, 834B. Thus, for example, a key may include two bores, one angledupwardly to direct a fixation screw upwardly into the tibia above thekey, and/or one angled downwardly to direct a fixation screw downwardlyinto the tibia below the key.

Looking next at FIGS. 36-38, there is shown an implant 800C also formedin accordance with the present invention. Implant 800C is generallysimilar to the implant 800 disclosed above, except that implant 800C hasa shear rib 890C on its base, laterally displaced from the two keys, aswill hereinafter be discussed in further detail. Furthermore, implant800C also provides an alternative approach for joining the posteriorgraft containment arm (GCA) to the base, and an alternative approach forjoining the anterior graft containment arm (GCA) to the base, as willhereinafter also be discussed in further detail. Furthermore, implant800C also provides a means for joining the distal end of posterior graftcontainment arm (GCA) 805C to the distal end of anterior graftcontainment arm (GCA) 815C, as will hereinafter also be discussed infurther detail.

More particularly, and still looking now at FIGS. 36-38, implant 800Ccomprises a posterior graft containment arm (GCA) 805C, a base 810C andan anterior graft containment arm (GCA) 815C. Preferably a bridge 892Cconnects the distal end of posterior graft containment arm (GCA) 805Cwith the distal end of anterior graft containment arm (GCA) 815C.

A shear rib 890C is formed in base 810C, laterally displaced from thetwo keys 820C, 825C.

Posterior graft containment arm (GCA) 805C includes a recess 893C, andbase 810C includes a shoulder 894C, whereby posterior graft containmentarm (GCA) 805C can mate with base 810C. Anterior graft containment arm(GCA) 815C includes a recess 895C, and implant base 810C includes ashoulder 896C, whereby anterior graft containment arm (GCA) 815C canmate with base 810C.

Posterior graft containment arm (GCA) 805C, and/or anterior graftcontainment arm (GCA) 815C, may include raised points or dimples 831C.

Keys 820C, 825C each include a bore 833C, 834C, respectively. Bores833C, 834C receive expansion thread fixation screws 865C for fixingimplant 800C to the tibia. The bores 833C, 834C may be axially alignedwith the longitudinal axes of keys 820C, 825C, respectively. The bores833C, 834C may also be configured to expand within the keyholes 85C, 90Cwhen inserted. Alternatively, the bores 833C, 834C may be arranged sothat they diverge from one another, downwardly and upwardly,respectively, to direct screws 865C deeper into the adjacent portions ofthe tibia. Keys 820C, 825C may also include external ribs 836C. Externalribs 836C may extend longitudinally or circumferentially. Keys 820C,825C may also be slotted (i.e., in a manner analogous to the slotsprovided in keys 820, 825 of implant 800), whereby to permit keys 820C,825C to expand when fixation screws 865C are received in bores 833C,834C.

Shear rib 890C is laterally offset from keys 820C, 825C. Shear rib 890Cprojects above and below the top and bottom surfaces of base 810C. Amongother things, it has been found that the provision of shear rib 890Cprovides, at the base of the implant, excellent load-bearingcharacteristics and substantial resistance to rotational and shearforces.

In order to provide appropriate keyholes 85C, 90C (FIG. 36) forreceiving keys 820C, 825C, and for providing a shear rib keyhole 897Cfor receiving shear rib 890C, a keyhole drill guide 400C (also sometimesreferred to as a “keystone guide”) may be used (FIGS. 39 and 40).Keyhole drill guide 400C is generally similar to the keyhole drill guide400 disclosed above (i.e. it uses a medial locating pin 480C,antero-medial surface locating point 485C), except that keyhole drillguide 400C has, in addition to its two guide holes 425C, 435C, a shearrib, guidehole 440C for forming shear rib keyhole 897C.

Implant 800C (and drill guide 400C) may be used in an open wedge, hightibial osteotomy in a manner which is generally similar to thatpreviously described with respect to implant 800 (and drill guide 400),including the above described end mill, except that the bridged graftcontainment unit, i.e., posterior graft containment arm (GCA) 805C,bridge 892C and anterior graft containment arm (GCA) 815C, is installedas a single construction. Furthermore, when drill guide 400C is used toform keyholes 85C and 90C, it is also used to form shear rib keyhole897C.

Providing implant 800C with two graft containment arms, e.g., posteriorgraft containment arm (GCA) 805C and anterior graft containment arm(GCA) 815C, is frequently preferred. However, in some circumstances, itmay be desirable to omit one or both of posterior graft containment arm(GCA) 805C and anterior graft containment arm (GCA) 815C. Thus, in onepreferred form of the invention, implant 800C comprises only base 810Cand omits both posterior graft containment arm (GCA) 805C and anteriorgraft containment arm (GCA) 815C.

Providing implant 800C with a pair of keys 820C, 825C is generallypreferred. However, in some circumstances, it may be desirable to omitone or the other of keys 820C, 825C. Furthermore, in othercircumstances, it may be desirable to provide more than two keys, e.g.,to provide three keys.

Furthermore, each of the keys 820C, 825C may include more than one bore833C, 834C. Thus, for example, a key may include two bores, one angledleftward to direct a fixation screw leftward into the tibia to the leftof the key, and/or one angled rightward to direct a fixation screwrightward into the tibia to the right of the key.

If desired, shear rib keyhole 897C can be formed using a conventionaldrill. More preferably, however, and looking now at FIGS. 40 and 41,shear rib keyhole 897C is formed using a shear rib end mill 445C. Shearrib end mill 445C generally comprises a shaft 450C having cutting edges455C, a corner radius 460C and flutes 465C. A relief area 470C is formedjust proximal to corner radius 460C. An end stop 475C limits, throughengagement with drill guide 400C, the depth of shear rib keyhole 897C.

It is also possible to use a modified form of posterior protector 500,and a modified form of positioning guide 100, when practicing thepresent invention.

More particularly, and looking now at FIGS. 42 and 43, there is shown aposterior protector 500A which is intended to be used in conjunctionwith an introducer 505A having a clamping collar 525A, a plunger 530A,alignment tabs 555A, and a handle 535A. Posterior protector 500Aincludes a flexible far tip 515A and stiff curved portion 520A. A bore540A extends through curved portion 520A. A base 545A is formed at theend of the curved portion 520A. Base 545A includes a bore 550A.Posterior protector 500A may be releasably secured to clamping collar525A by positioning base 545A in clamping collar 525A and advancingplunger 530A against the proximal end of posterior protector 500A.

Posterior protector 500A may be used in conjunction with the positioningguide 100A shown in FIGS. 44 and 45. Positioning guide 100A includes, inaddition to its normal elements, an introducer alignment pin 170A.Introducer alignment pin 170A preferably extends at a right angle tomedial locating pin 140A. In use, and looking now at FIGS. 46-48,introducer 505A is used to position posterior protector 500A so that fartip 515A and curved portion 520A are properly positioned relative to thepatient's anatomy, and so that medial locator pin 140A extends throughbore 540A and introducer alignment pin 170A extends through bore 550A.The plunger 530A also seats in the introducer pocket 565A. Theintroducer tab slot 560A is configured for the introducer tabs 555A.Then introducer 505A is disengaged from posterior protector 500A (FIG.46), leaving posterior protector 500A extending across the posteriorcortex of the tibia, interposed between the tibia and the delicateneurological and vascular structures located at the back of the knee.Thereafter a cutting guide 600A may be secured to positioning guide 100A(FIG. 47) using a cutting guide thumbscrew 605A, and saw blade 625A isused to form osteotomy cut 20. The position of the cutting guide 600A isset by alignment fingers 565A.

Antero-Lateral Osteotomies

In the foregoing description, the present invention is discussed in thecontext of performing an open wedge osteotomy using an antero-medialapproach so as to effect a medial opening wedge osteotomy. Of course, itshould be appreciated that the present invention may also be used inantero-lateral approaches to effect a lateral opening wedge osteotomy,or in other approaches, which will be well known to those skilled in theart.

MODIFICATIONS

It will be understood that many changes in the details, materials, stepsand arrangements of parts, which have been herein described andillustrated in order to explain the nature of the invention, may be madeby those skilled in the art without departing from the principles andscope of the present invention.

What is claimed is:
 1. A method for performing an open wedge osteotomycomprising: cutting a bone along a cutting plane to form a cut, with thecut terminating at a boundary line; forming at least two keyholes in thetibia adjacent to the cut, wherein the two keyholes are laterally offsetfrom one another; moving the bone on either side of the cut apart so asto form a wedge-like opening in the bone; and positioning a wedge-shapedimplant in the wedge-shaped opening created in the tibia, wherein thewedge-shaped implant comprises at least two keys, laterally offset fromone another, and further wherein the at least two keys are disposed inthe at least two keyholes formed in the tibia.
 2. A method according toclaim 1, wherein the wedge-shaped implant comprises at least twoseparate components.
 3. A method according to claim 1, wherein thewedge-shaped implant comprises three separate components.
 4. A methodaccording to claim 3, wherein the wedge-shaped implant comprises: a basecomponent; a posterior component; and an anterior component.
 5. A methodaccording to claim 4, wherein the at least two keys are disposed on thebase.
 6. A method according to claim 1, wherein each of the at least twokeys includes an interior bore for receiving a fixation screw.
 7. Amethod according to claim 6, wherein each interior bore is axiallyaligned with the longitudinal axis of its host key.
 8. A methodaccording to claim 7, wherein each interior bore is angled to direct thefixation screw into the adjacent bone.
 9. A method according to claim 1,wherein each of the at least two keys are slotted longitudinally so asto permit expansion when a fixation screw is received by the key.
 10. Amethod according to claim 1, wherein each of at least two keys includesexternal ribs to facilitate fixation of the keys relative to the key.11. A method according to claim 10, wherein the external ribs extendlongitudinally along the keys.
 12. A method according to claim 10,wherein the external ribs extend circumferentially along the keys.
 13. Amethod according to claim 2, wherein the wedge-shaped implant isassembled prior to positioning in the tibia.
 14. A method according toclaim 2, wherein the wedge-shaped implant is assembled after positioningin the tibia.
 15. A method according to claim 1, wherein each keyincludes at least two interior bores for receiving a fixation screwtherein.
 16. A method for performing an open wedge osteotomy comprising:cutting a bone along a cutting plane to form a cut, with the cutterminating at a boundary line; forming at least two keyholes in thetibia adjacent to the cut, wherein the two keyholes are verticallyoffset from one another; forming a shear rib keyhole in the tibiaadjacent to the cut, wherein the shear rib keyhole is laterally offsetfrom the at least two keyholes; moving the bone on either side of thecut apart so as to form a wedge-like opening in the bone; andpositioning a wedge-shaped implant in the wedge-shaped opening createdin the tibia, wherein the wedge-shaped implant comprises at least twokeys, vertically offset from one another, and a shear rib, laterallyoffset from the at least two keys, and further wherein the at least twokeys are disposed in the at least two keyholes formed in the tibia, andthe shear rib is disposed in the shear rib keyhole formed in the tibia.17. A method according to claim 16, wherein the wedge-shaped implantcomprises at least two separate components.
 18. A method according toclaim 16, wherein the wedge-shaped implant comprises three separatecomponents.
 19. A method according to claim 18, wherein the wedge-shapedimplant comprises: a base component; a posterior component; and ananterior component.
 20. A method according to claim 19, wherein the atleast two keys are disposed on the base.
 21. A method according to claim16, wherein each of the at least two keys includes an interior bore forreceiving a fixation screw.
 22. A method according to claim 21, whereineach interior bore is axially aligned with the longitudinal axis of itshost key.
 23. A method according to claim 22, wherein each interior boreis angled so as to direct the fixation screw into the adjacent tibia.24. A method according to claim 16, wherein each of the at least twokeys are slotted longitudinally to permit expansion when a fixationscrew is received by the key.
 25. A method according to claim 16,wherein each of at least two keys includes external ribs to facilitatefixation of the keys relative to the key.
 26. A method according toclaim 25, wherein the external ribs extend longitudinally along thekeys.
 27. A method according to claim 25, wherein the external ribsextend circumferentially along the keys.
 28. A method according to claim18, wherein the wedge-shaped implant is assembled prior to positioningin the tibia.
 29. A method according to claim 18, wherein thewedge-shaped implant is assembled after positioning in the tibia.
 30. Amethod according to claim 17, wherein each key includes at least twointerior bores for receiving a fixation screw therein.